Method of and apparatus for supplying powdery material

ABSTRACT

A method of and an apparatus for supplying a powdery material to a workpiece to be processed thereby. According to the method, the powdery material is discharged from a hopper and metered, and then fed into a tube extending in the vicinity of the workpiece. Ultrasonic vibrations are imparted to the tube to supply the powdery material to a portion to be processed of the workpiece while the amount of the supplied powdery material is being detected. The apparatus includes a hopper for storing the powdery material, the hopper having an outlet, a tube extending from the outlet to a position adjacent to the workpiece for conveying the powdery material therethrough, and an ultrasonic vibrating device mounted on the tube for imparting ultrasonic vibrations to the tube, and a device mounted on the tube for detecting the amount of the powdery material supplied through the tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of and an apparatus forsupplying a powdery material such as of a hard metal to a molten poolwhen forming a remelted and hardened layer on a surface of a cast ironmember.

2. Description of the Prior Art

Cast iron members such as camshafts employed in internal combustionengines are required to have surface layer such as a sliding surfacewhich is of a better wear-resistance and pitting-resistance than therest of the cast iron member. To meet such a requirement, the applicanthas proposed in a earlier application to remelt the surface layer, addpowder of a hard metal to the molten pool, and chill the molten area tothereby form a hard layer that is highly resistant to wear and pitcorrosion.

In the above remelting and hardening process, it is general to add themetal powder to the molten pool by supplying the metal powder through asupply tube to a burner nozzle while the metal powder is floating in dryair or an inert gas. However, the metal powder as it is supplied underthe floating condition tends to be deposited on the inner wall surfaceof the supply tube, with the result that the substantial inside diameterof the tube is reduced, making it impossible to feed the metal powderstably. As a consequence, the metal powder is supply in irregularquantities which adversely affect the quality of the remelted members.

A conventional solution to the above difficulties has been to plate theinner wall surface of the supply tube or to construct the supply tube ofa material having a low coefficient of friction. These prior measureshowever have failed to sufficiently prevent metal powder from beingdeposited on the inner wall surface of the supply tube.

SUMMARY OF THE INVENTION

The present invention has been made in view of the aforesaid drawbacksof the prior art.

It is an object of the present invention to provide a method ofsupplying a powdery material such as of a hard metal stably through asupply tube without causing deposits and clogging therein toward amolten pool formed by remelting a surface layer of a cast iron member,thus producing a hardened surface layer of uniform and stable quality,which is highly resistant to wear and pitting.

Another object of the present invention is to provide a powdery materialsupplying apparatus by which the above method can be carried out.

According to the present invention, there is provided a method ofsupplying a powdery material to a workpiece to be processed thereby,comprising the steps of discharging the powdery material from storagemeans, feeding the powdery material discharged from the storage meansinto tube means extending in the vicinity of the workpiece, andultrasonically vibrating the tube means for supplying the powderymaterial therethrough to the workpiece.

According to the present invention, there is also provided an apparatusfor supplying a powdery material to a workpiece to be processed thereby,comprising storage means for storing the powdery material, the storagemeans having an outlet, tube means extending from the outlet to aposition adjacent to the workpiece for conveying the powdery materialtherethrough, and an ultrasonic vibrating device mounted on the tubemeans for imparting ultrasonic vibrations to the tube means.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an apparatus for supplying a powderymaterial according to the present invention;

FIG. 2 is a perspective view of a metering device in the apparatus ofFIG. 1;

FIG. 3 is a cross-sectional view of a device for detecting the suppliedamount of a powdery material;

FIG. 4 is a fragmentary enlarged cross-sectional view of the deviceshown in FIG. 3;

FIG. 5 is a cross-sectional view taken along line V--V of FIG. 4; and

FIG. 6 is a diagrammatic view of an apparatus for remelting andhardening a cast iron member, in which the powdery material supplyingapparatus of the present invention can be incorporated.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows in cross section an apparatus for supplying a powderymaterial according to the present invention. The apparatus includes apowdery material feeding device 1 composed of a closed housing 2including a bottom 3 on which there is mounted a pipe 4 for supplyingtherethrough an inert gas such as an argon gas into the housing 2 tokeep the interior thereof under a positive pressure.

A hopper 6 storing a powdery material 5 therein is disposed in thehousing 2. The powdery material 5 may comprise a hard metal such as Cr,Mo, Ni, W, V, or Nb, or a compound thereof which is reduced to a powderystate. The hopper 6 includes a funnel-shaped lower portion having anoutlet 6a positioned above a device 7 for metering the powdery material5. As shown in FIGS. 1 and 2, the metering device 7 is composed of amotor 8 disposed below the bottom 3 and having a rotatable shaft 9extending upwardly through the bottom 3 and having an upper endpositioned beneath the outlet 6a of the hopper 6 and supporting aturntable 10 rotatable in a horizontal plane.

As shown in FIG. 2, a vertically movable base 11 positioned upwardly ofa peripheral edge of the turntable 10 includes a bracket 12 on whichthere is pivotally mounted a metering blade 13 lying in a vertical planeand elongated horizontally, the metering blade 13 being spaced a smallclearance from the upper surface of the turntable 10 and angularlymovable in the horizontal direction. The metering blade 13 is angularlyadjustable in the horizontal direction with respect to the base 11 by aposition adjusting screw 14 fixed to the base 11. A funnel-shapedreceiver 15 is mounted on the bottom 3 below the metering blade 13 withthe turntable 10 interposed therebetween.

Referring back to FIG. 1, another metering blade 113 which is alsovertically positionally adjustable is disposed above the turntable 10 indiametrically opposite relation to the metering blade 13. The meteringblade 113 serves to level the powdery material 5 supplied from theoutlet 6a onto the turntable 10.

The powdery material 5 stored in the hopper 6 is supplied through theoutlet 6a onto the turntable 10. When the turntable 10 is rotated by themotor 8, the powdery material 5 on the turntable 10 is scraped by themetering blade 13 off the turntable 10 into the receiver 15. The amountof the powdery material 5 thus supplied into the reciever 15 can beadjusted by either vertically moving the base 11 to vary the clearancebetween the metering blade 13 and the upper surface of the turntable 10,or turning the metering blade 13 or 113 horizontally with respect to theturntable 10.

The funnel-shaped receiver 15 has a lower tubular portion extendingvertically through and supported by the bottom 3. The lower tubularportion of the receiver 15 has a lower end 15a fitted in a vibrator 17of an ultrasonic vibrating device 16. The vibrator 17 has a passage 18defined vertically therethrough and having an upper larger-diameterrecess in which the lower end 15a of the receiver 15 is fitted. Thepassage 18 also has a lower larger-diameter recess in which an upper endof an inverted Y-shaped joint 19 is fitted. The passage 18 has an insidediameter equal to the inside diameter of the lower tubular portion ofthe receiver 15 and also to the inside diameter of a passage 19a definedin the joint 19.

The joint 19a has a pair of divided tubes 19b, 19b to which the upperends 20a, 20a of supply tubes 20, 20 are connected, respectively. Eachof the supply tubes 20, 20 is made of stainless steel or a ceramicsmaterial, and has a lower end 20b extending through and held by a shieldcap 22 of a plasma torch nozzle 21. The lower ends 20b of the supplytubes 20, 20 supported by the shield cap 22 have their axessubstantially crossing the central axis of a passage 24 defined in anozzle tip 23 for blowing a plasma gas downwardly therethrough.

A device 25 for detecting the amount of the supplied powdery material ismounted on the intermediate portion of each of the supply tubes 20, 20.As shown in FIGS. 3, 4, and 5, the device 25 includes a body 26comprising a vertically elongate tubular member having on itsintermediate portion a pair of arms 27, 27 projecting laterallyoutwardly away from each other. The body 26 has upper and lowerlarger-diameter holes 28, 29 defined vertically therein and anintermediate smaller-diameter hole 30 defined vertically therein andcommunicating with the upper and lower larger-diameter holes 28, 29. Thearms 27, 27 have transverse holes 31, 31, respectively, defined thereinand having ends opening into the small-diameter hole 30 and oppositeends opening outwardly. The upper larger-diameter hole 28 has an uppertapered end 28a flaring upwardly, and the lower larger-diameter hole 29has a lower tapered end 29a flaring downwardly. The intermediatesmaller-diameter hole 30 has a tapered upper end 30a flaring upwardly.

Sealing plugs 32, 33 are force-fitted respectively in the upper andlower tapered ends 28a, 29a of the body 26. Caps 34, 35 are threadedrespectively over externally threaded surfaces of the upper and lowerends of the body 26 to keep the sealing plugs 32, 33 pushed in thetapered ends 28a, 29a. The sealing plugs 32, 33 have through holes 32a,33a axially defined respectively therein with the supply tube 20force-fitted in and retained by the through holes 32a, 33a. The caps 34,35 have holes 34a, 35a defined respectively therein and having adiameter larger than that of the supply tube 20, which extends throughthe holes 34a, 35a. In assembly, the supply tube 20 is inserted axiallythrough the body 26 and extends through the holes 32a, 33a in thesealing plugs 32, 33, and then the caps 34, 35 are threaded over theends of the body 26. The body 26 is now supported on the supply tube 20.When the supply tube 20 is inserted in the body 26, the supply tube 20should be adjusted to bring a pair of diametrically opposite windows20a, 20a defined in the supply tube 20 into confronting relation to thetransverse holes 31, 31 in the arms 27, 27, respectively.

Tubular sealing plugs 36, 36 are inserted respectively in the transverseholes 31, 31, and caps 37, 37 are threaded respectively over the arms27, 27. An optical fiber 39 extending from a light-emitting device 38 isforce-fitted in a through hole 36a defined axially in one of the sealingplugs 36, and another optical fiber 41 extending from a photodetector 40is force-fitted in a through hole 36a defined axially in the othersealing plug 36. The optical fibers 39, 41 have ends projecting from thesealing plugs 36, 36 in confronting relation to the windows 20a, 20a,respectively, in the supply tube 20.

A pipe 42 is attached to an upper portion of the side wall of the body26 in communication with the upper larger-diameter hole 28 for supplyinga back-pressure generating inert gas such as an argon gas into thelarger-diameter hole 28. Another pipe 43 is attached to a lower portionof the side wall of the body 26 in communication with the lowerlarger-diameter hole 29 for discharging a leaked amount of powderymaterial from the body 26.

Operation of the powdery material supplying apparatus thus constructedis as follows: The ultrasonic vibrating device 16 has a piezoelectricelement or the like for actuating the vibrator 17 with ultrasonic energyto vibrate the vibrator 17. The powdery material 5 supplied from thehopper 6 into the receiver 15 by the metering device 7 is fed into thesupply tubes 20 while the powdery material 5 is being vibrated by thevibrator 17 vibrated by the ultrasonic vibrating device 16. The powderymaterial 5 as it enters the supply tubes 20 is conveyed by gravity andunder the pressure of the inert gas supplied from the pipe 4 mounted onthe bottom 3, to the plasma torch nozzle 21 in which the powderymaterial 5 is fed into a plasma arc 44 generated by the plasma torchnozzle 21. The powdery material 5 such as of a hard metal is then sealedin the plasma arc 44 and injected into a molten pool 46 formed on thesurface layer of a cast iron member 45, whereupon the powdery material 5is uniformly dispersed or melted in the molten pool 46 to remelt thecast iron member 45. Since the entire passageway including the supplytubes 20 is vibrated by the vibrator 17, the powdery material 5 flowingtherethrough is prevented from being deposited on the inner wallsurfaces of the passage 18 in the vibrator 17, the passage 19a in thejoint 19, and the tubes 20, 20. Even if some powdery material 5 sticksto the inner wall surfaces, it will soon be shaked off by the vibratingpassageway and join the powdery material 5 flowing therethrough. Thestable and constant supply of the powdery material 5 through the supplytubes 20, 20 is effective in producing remelted and hardened products ofuniform quality. Since the passageway vibrates ultrasonically with smallamplitudes, no damage will be caused to the joint 19 and the tubes 20which may be of a rigid material. The powdery material 5 can thereforebe conveyed smoothly and reliably without clogging to the molten pool46.

While in the illustrated embodiment the ultrasonic vibrating device 16is connected to the receiver 15 between the powdery material feedingdevice 1 and the supply tubes 20, 20, the ultrasonic vibrating device 16may also be installed somewhere on the supply tubes 20, 20. Morespecifically, where the tubes 20, 20 are considerably long, anultrasonic vibrating device 160 of the same construction as that of theultrasonic vibrating device 16 may also be mounted on each of the supplytubes 20, 20 downstream of the joint 19 for more effective prevention ofdeposition of the powdery material 5 on the inner wall surfaces of thesupply tubes 20, 20.

The device 25 for detecting the amount of the supplied powdery material5 can ascertain the amount of the powdery material 5 supplied througheach of the supply tubes 20, 20 by measuring the amount of lighttransmitted from the light-emitting device 38 and detected by thephotodetector 40 through the windows 20a, 20a. The photodetector 40issues a signal as a function of the amount of the powdery material 5flowing through the supply tube 20, and such a signal may be processedand sent to an indicator for visual display. The signal may also beemployed to control operation of the metering device 7 for varying theamount of the powdery material 5 to be supplied from the feedingdevice 1. Although the closed space S (FIG. 4) communicates with theinterior of the supply tube 20 through the windows 20a, 20a, only asmall amount of powdery material 5 leaks from the supply tube 20 via thewindows 20a, 20a because the inert gas supplied through the pipe 42develops a higher back pressure in the closed space S than the pressurein the supply tube 20. Any leaked amount of powdery material 5 isdischarged out of the body 26 through the discharge pipe 43 and thenrecovered.

As an alternative, the powdery material 5 may be prevented from leakingout of the supply tube 20 by closing the discharge pipe 43 andintroducing the back-pressure gas from the pipe 42 into the supply tube20 through the windows 20a, 20a.

Inasmuch as the ends of the optical fibers 36, 38 are spaced from thewindows 20a, 20, respectively, no powdery material will be deposited onthe ends of the optical fibers 36, 38, and hence optical measurementsmade by the device 25 will remain stable against errors for a longperiod of time.

Although the device 25 has been shown as being incorporated in theapparatus for remelting and hardening cast iron members with a plasmaarc, the device 25 may be employed in various apparatus for conveyingpowdery materials. The optical fibers 39, 41 may be dispensed with, andthe light-emitting device and photodetector may be disposed in place ofthe optical fibers 39, 41 for direct transmission and reception ofoptical signals.

The results of an experiment conducted on an apparatus for supplying apowdery material constructed according to the present invention will bedescribed below. The supply tubes 20 were formed of stainless steel, andhad an outside diamter of 2 mm and an inside diameter of 1.5 mm. Theargon gas was supplied from the pipe 4 at a rate of 1 liter/min. Thepowdery material conveyed had a particle size ranging from 1 micron to50 microns, and was fed at a rate of 0.5 g/min. The ultrasonic vibrator17 vibrating at a frequency of 2 KHz and powered by 300 W was held incontact with the supply tubes 20, 20 to impart ultrasonic vibrations tothe supply tubes 20, 20. The ultrasonic vibrator 1 was energized for 1minute to convey the powdery material and then de-energized. Then, thesupply tubes 20, 20 were inspected for any residual powdery material,but no powdery material was left in the supply tubes 20, 20. When thesupply tubes 20, 20 were not ultrasonically vibrated, and the powderymaterial was conveyed therethrough for 1 minute, 0.18 g of powderymaterial remained in the supply tubes 20, 20.

An apparatus for remelting and hardening a cast iron material, in whichapparatus the powdery material supplying apparatus of the invention canbe incorporated, will be described with reference to FIG. 6.

The apparatus shown in FIG. 6 serves to remelt and harden cams 101 on aworkpiece or camshaft 100. The axial ends of the camshaft 100 aresupported respectively by a chuck 102 and a center 103, and the camshaft100 is held in position by a presser cylinder 104 coupled to the center103 and pressing the camshaft 100 in the axial direction. The chuck 102is rotated by a motor 105 to rotate the camshaft 100. A plasma torch 106movable axially along the camshaft 100 is positioned above a desired oneof the cams 101. The plasma torch 106 is vertically movably supported bya support frame 108 of a holder 107. The support frame 108 is held inthreaded engagement with a feed screw 110 rotated about its own axis bya motor 109. In operation, the camshaft 100 is rotated by the motor 105,the plasma torch 106 is vertically moved to follow the cam profile ofthe cam 101 to be processed with a constant clearance kept between thecam profile and the nozzle of the plasma torch 106. Over the desired cam101 to be treated, the plasma torch 106 is reciprocally moved axiallyalong the camshaft 100 so as to follow a meandering path over the camprofile while the camshaft 100 is rotated about its own axis, therebyremelting and hardening the cam surface of the cam 101. The plasma torch106 is horizontally moved by the feed screw 110 along the camshaft 100for successively processing the cams 101. In FIG. 6, there are eightcams 101 on the camshaft 100, and two plasma torches 106 employed.Therefore, four cams 101 are remelted by each of the plasma torches 106.

The plasma torch is shown in greater detail in FIG. 1. The plasma torchhas the nozzle tip 23 disposed in the hollow shield cap 22 with apassage 47 defined between the nozzle tip 23 and the shield cap 22 forpassage of a shield gas such as an inert gas therethrough. The passage24 for allowing a working gas such as an argon gas to pass therethroughis defined centrally in the nozzle tip 23 and surrounded by a coolantpassage 48 defined in the nozzle tip 23. An electrode 49 as of tungstenis positioned in the passage 24 and electrically connected to a powersupply 112 (FIG. 6) by a cord 121.

The supply tubes 20, 20 extend obliquely through the lower wall portionof the shield cap 22. The supply tubes 20, 20 are made of a materialhaving a small coefficient of friction, such as stainless steel. Thesupply tubes 20, 20 are symmetrically attached to the shield cap 22 withtheir distal ends inclined a prescribed angle with respect to the axis Nof the plasma torch nozzle 21 extending in alignment with the axis ofthe passage 24. As described above, the supply tubes 20, 20 areconnected to the powdery material device 1 for supplying the powderymaterial of metal to the molten pool formed when the cam 101 is meltedby the plasma arc, to thereby form a hard alloy layer on the camsurface.

The apparatus illustrated in FIG. 6 also includes an electronic controlunit 122 for controlling the motors 105, 109, a motor (not shown) housedin the holder 107 for vertically moving the plasma torch 106, the powersupply 112, the powdery material supplying apparatus 115, the ultrasonicvibrating device 16, and the detecting device 121.

Although there have been described what are at present considered to bethe preferred embodiments of the present invention, it will beunderstood that the invention may be embodied in other specific formswithout departing from the spirit or essential characteristics thereof.The present embodiments are therefore to be considered in all aspects asillustrative, and not restrictive. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription.

What is claimed is:
 1. A method of supplying a powdery material to aworkniece to be processed thereby, comprising the steps of:(a)discharging the powdery material from storage means; (b) feeding thepowdery metal material discharged from said storage means into the tubemeans extending into the shield cap of a plasma torch nozzle in thevicinity of the workpiece; and (c) ultrasonically vibrating said tubemeans for supplying the powdery material therethrough through saidshield cap to said workpiece.
 2. A method according to claim 1,including the step of metering said powdering material before it isdischarged from said storage means into said tube means.
 3. A methodaccording to claim 1, including the step of detecting the amount of thepowdery material when it is supplied through said tube means.
 4. Amethod according to claim 3, wherein said amount of the powdery materialis detected by a light-emitting device and a photodetector.
 5. A methodaccording to claim 1, including the steps of:(d) melting the surface ofsaid workpiece with plasma arc; and (e) supplying said powdery materialfrom said tube means through said shield cap into said plasma arc sothat the powdery material is charged into a molten pool on saidworkpiece.
 6. An apparatus for supplying a powdery metal material to aworkpiece to be processed thereby, comprising;(a) storage means forstoring the powdery material said storage means having an outlet; (b)tube means extending from said outlet to a shield cap of a plasma torchnozzle adjacent to said workpiece for conveying the powdery materialtherethrough and through said shield cap; and (c) an ultrasonicvibrating device mounted on said tube means for imparting ultrasonicvibrations to said tube means.
 7. An apparatus according to claim 6,including metering means disposed between said outlet and said tubemeans for metering the powdery material fed into said tube means.
 8. Anapparatus according to claim 7, wherein said metering means comprises aturntable disposed below said outlet and rotataing in a horizontalplane, and a metering blade spaced a small clearance from an uppersurface of said turntable and lying in a substantially vertical plane.9. An apparatus according to claim 8, wherein said metering blade isvertically movable with respect to said turntable.
 10. An apparatusaccording to claim 8, wherein said metering blade is angularly movablehorizontally.
 11. An apparatus according to claim 6, including meansmounted on said tube means for detecting the amount of the powderymaterial supplied through said tube means.
 12. An apparatus according toclaim 11, wherein said tube means has a tubular wall, said detectingmeans comprising a pair of windows defined in said tubular wall of saidtube means in diametrically opposite relation, a tubular body having aclosed chamber therein around said tube means at said window, and alight-emitting member and a photodetecting member disposed in said bodyin confronting relation to said windows, respectively.
 13. An apparatusaccording to claim 12, wherein said detecting means includes a secondtube connected to said tubular body for supplying a back-pressuregenerating gas into said closed chamber to keep a pressure in saidclosed chamber at a level higher than the pressure in said tube means.14. An apparatus according to claim 6, wherein said tube means comprisesa receiver for receiving said powdery material discharged into said tubemeans, and a tube for guiding the powdery material from said receiver tothe position adjacent to said workpiece.
 15. An apparatus according toclaim 14, wherein said ultrasonically vibrating device is mounted on atleast one of said receiver and said tube.
 16. An apparatus according toclaim 14, wherein said ultrasonically vibrating device is connectedbetween said receiver and said tube.